Wireless communications systems normally include more access terminals, e.g., mobile communications devices, than access routers such as base stations. For a communications system to be commercially successful the access terminals need to be of reasonable cost with lower cost access terminals making the terminals affordable to a larger number of customers than high priced access terminals. The drive to keep individual access terminals affordable to a wide range of individual users results in price pressure which encourages the use of inexpensive components in access terminals. In contrast, since base stations are used by multiple users, the cost of a base station is less price sensitive. As a result, more accurate and often more costly components are used in base stations than access terminals.
Thus, for cost reasons, e.g., relatively inexpensive and slightly inaccurate voltage controlled oscillators and/or other circuits may be used in access terminals. This can result in access terminals exhibiting clock and/or frequency errors which can normally be corrected for by adjusting a control input, e.g., voltage, to a voltage controlled oscillator or other component assuming sufficient input to allow for detection of the inaccuracy. In communications systems which include base stations with high quality components, such as most commercial cellular systems, to avoid interference from access terminals due to the inaccuracy of the access terminal components, access terminals normally receive timing and/or other signals from an access router in the cellular network which are then used by the access terminal to detect and/or adjust for inaccuracies in the access terminal. Based on the received signals, whether they be broadcast pilot signals, broadcast beacon signals, or specific signals directed to an individual access terminal as part of a closed loop control process involving an access router, an access terminal will normally perform a correction operation, e.g., an adjustment, so that its timing and/or frequency of operation matches that of an access router in the cellular system. Such adjustments may be made by altering a voltage on a voltage controlled oscillator and/or making other adjustments so that the access terminal operates in a more reliable and accurate manner than if such adjustments were not made based on signals received from an access router in the cellular system.
While highly accurate access routers are normally present in most commercial cellular systems using licensed spectrum, e.g., a licensed frequency band, in non-licensed spectrum access routers may be, e.g., low cost base stations which may not be any more accurate than the access terminals with which they interact. Furthermore, in peer to peer systems access routers may be omitted entirely and/or peer to peer devices may not transmit signals intended to be used as accurate timing or frequency reference signals. Such an approach may be acceptable from a cost perspective in the case of non-licensed spectrum since the user is not paying for the spectrum and some overall inefficiency resulting from interference due to device inaccuracies may not be of concern to an individual user of the unlicensed spectrum. However, the importance of a loss in overall communications throughput in a system due to use of inexpensive access terminals, access routers and/or peer to peer devices begins to increase when such devices are used in licensed spectrum because of the cost of the licensed spectrum. The importance of a loss in overall communications system throughput also begins to be more important when the unlicensed spectrum begins to become more congested making it in the general interest of the users of the unlicensed spectrum to decrease the interference caused to other devices so that communications in the unlicensed spectrum will become more reliable.
In view of the above, it should be appreciated that there is a need for methods and apparatus which would allow low cost communications devices to be used while still obtaining the advantages of adjustments made based on reliable and accurate signals which maybe, for example, transmitted by an access router in a cellular system using licensed spectrum.